The First Tropical Wave of the Season in Bermuda


A surge of moisture is on the way for this afternoon as a weak surface trough approaches the island. This trough of low pressure is skirting the southern edge of the Bermuda-Azores High pressure ridge and has been invigorated by the Tropical Upper Tropospheric Trough (TUTT); a transient feature in the mid latitudes. This ‘TUTT’ is a high altitude area of cooler, converging, and sinking air and it usually coincides with the southwestern end of the the Bermuda-Azores High. On the edges of the TUTT, its anti-clockwise circulation creates strong wind shear that is bad for hurricane development, but, in association with the cooler air, it can help weak systems produce more convection – which is what is happening in this scenario.

Scattered showers and possibly thunderstorms are expected to increase in coverage this afternoon and evening and last at least through Friday night as the trough passes. Some areas will likely get larger amounts of rain than others even though Bermuda is so small. This is because the showers are going to be scattered and hit and miss. Additionally, unless a heavy shower sits over you, I wouldn’t really expect huge accumulations of rainfall. The Bermuda-Azores High should start to regain control of the area by the weekend, and will be firmly in place again for the beginning of the work week with more settled weather.

Recently heat indices have frequently been between 90F and 105F around the island at both the Bermuda Weather Service Automated Weather Observing Stations and at various Personal Weather Stations. The heat index is found by factoring the humidity into the air temperature to determine what it feels likeExtreme caution should be taken when physically exerting yourself in this type of heat. This heat should continue through the rest of the week, although any rain associated with the trough will cool things off.

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